<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>

        const p1 = () =>{
            return new Promise((resolve, reject) => {
                setTimeout(() =>{
                    console.log('p1触发了');
                    resolve('a')
                },1000)
            })
        }
        const p2 = () =>{
            return new Promise((resolve, reject) => {
                setTimeout(() =>{
                    console.log('p2触发了');
                    resolve('b')
                },500)
            })
        }
        const p3 = () =>{
            return new Promise((resolve, reject) => {
                setTimeout(() =>{
                    console.log('p3触发了');
                    resolve('c')
                },1500)
            })
        }

        p1()
        .then((res)=>{
            console.log(res); // a
            return p2()
        })
        .then((res)=>{
            console.log(res); // b
            return p3()
        })
        .then((res)=>{
            console.log(res); // c
            console.log('最后的触发');
        })
    </script>
</body>
</html>